I have had a standard mobile phone for 6 years,only used for infrequent calls for taxi and so it has a baht credit of some 4000 baht.....12call network which I understand is AIS

Am thinking of getting a smart phone.
is it going to be possible for my credit on my old phone to be transfered to the smart phone and so would get internet ect

which would use up the baht's much quicker

Your credit will go with your sim card.

Just put your sim into the new phone. If it's too big, ask your operator for one that fits. Or get somebody to cut it down

^ Have you registered your phone number yet? You need to do before June, or you will probably lose your money if you don't. Whilst you are there (AIS shop) you can ask them.

You can transfer your balance to your new sim card, as long it's also AIS.

See here: http://www.ais.co.th/12call/en/balance-validity-transfer.html

You can transfer your balance to your new sim card, as long it's also AIS.

See here: http://www.ais.co.th/12call/en/balance-validity-transfer.html

If the OP is keeping the same number and just replacing the sim, then the above link is not applicable. That info is for transferring credit to a different AIS prepaid number.

As posted above, credit is tied to the number, replacing a sim card without getting a new number keeps the existing credit in play.

As said changing phone while keeping (cutting down?) the SIM card (and phonenumber) does not affect the credit.

Registering the SIM/phone number under your name is requested until 31 July 2015.

(nobody can tell exactly what happens after that?)

If you can take the device and the old sim into an AIS service centre, then there will be no need to cut it down yourself.

They will replace it FOC without a fuss.

The new sim they give will be pre-cut into either full sim + mini or full sim + nano, you just snap the smaller sim out.

At the same time, you can ask them to detail the plan/packages your old sim is on, and work out whether to change plans or not.

I do not know if this applies to you but there are certain "legacy plans", very attractively priced plans offered years ago that give very good terms and rates. If you happen to have one of these older plans, don't let them talk you into replacing it with a newer, less attractive plan.

Maybe another reader more knowledgeable than I can elaborate more on these legacy plans.